1. Field of the Invention
This invention relates to an automatic seat belt system, and especially to an improvement to the drive member of such an automatic seat belt system.
2. Description of the Prior Art
In an automatic seat belt system, a runner on which one portion of a webbing is fastened is displaceable along a guide rail arranged along the body of an automobile while being guided by the same guide rail. The runner is driven by a drive means for example in association with the opening or closure of a door so that the runner moves along the guide rail to render the webbing displaceable between an occupant restraining position and an occupant non-restraining position. As such drive members, drive tapes made of synthetic resins, such as those described in U.S. Pat. No. 4,313,622 issued Feb. 2, 1982 to Ichiro Suzuki et al, have found wide-spread commercial utility because inter alia they may be fabricated at lower costs and they produce less noise upon their operations compared with conventional wires, for example, those disclosed in U.S. Pat. No. 4,274,658 issued June 23, 1981 to Juichiro Takata. As materials for such drive tapes, polyester-base resins have conventionally been used as described for example in German Offlenlegungsschrift No. 22 15 053 assigned to Metallwerk Max Brose GmbH & Co. and laid-open to the public on Oct. 23, 1980. However, drive tapes made of such polyester-base resins require high fabrication costs. In addition, the resistance of such drive tapes are not very strong against tensile or compression forces. Therefore, it is indispensable to make the widths and thicknesses of such drive tapes greater. Such drive tapes are hence accompanied by such inherent drawbacks that their guide rails, namely, the seat belt systems become larger correspondingly and due to their large widthwise dimensions, their sliding resistance increases to considerable extents when the drive tapes are arranged along the bodies of their respective automobiles in such a way that they are bent in widthwise directions.